Originally, Nippon Ichi Software considered making The Witch and the Hundred Knight an open-world game, but this was ultimately scrapped in favor of focusing on the game's 3D graphics technology.

The expanded version of myPOPGOES has a challenge named "Mini-P," which makes pizzas cook faster, but restore less hunger. This is a reference to one of Scott Cawthon's characters from the 2015 troll game FNaF World: Halloween Edition, also named Mini-P, which has the appearance of William Afton's "Purple Guy" sprite, just smaller and with red glowing eyes.

The title card for the Underworld stage contains a typo as the word "Summoning" is instead spelled as "Summning". This typo is only present in the USA and PAL versions.

After killing the Swirl in mid-flight, a black vertical line appears across the spot where the Swirl was shot. This line is referred to under the Helpful Hints section in the game's manual as the "Ghost of Yars" and warns the player to stay off its "mean streak". If the Yar is in the lower third of the screen and the black spot on its back is aligned across the vertical line at the moment the explosion vanishes, the game ends and goes into the "Game Select" screen with "HSWWSH" in place of the player's score. These are the mirrored initials of the game's creator Howard Scott Warshaw.

In 2024, a hidden variation of the Konami Code was discovered in the game that allows you to unlock all characters and costumes from the start. To activate it, on the title screen, press C-Up four times/C-Down four times/C-Left/C-Left/C-Right/C-Right/C-Left/C-Left/C-Right/C-Right/L/R/Z.

While Mario's mustache, red shirt and blue overalls were described by Miyamoto as the result of technical limitations, there's a possibility that they were also inspired by an issue of the Japanese men's fashion magazine Popeye, named after the fictional character that Mario was already partly inspired by. The March 1980 issue of Popeye magazine features cover art of a man with a mustache wearing a red shirt with blue overalls.

Mecarobot Golf is a partial reskin of Birdie Try, a generic, non-robot-themed golf game starring Japanese professional golfer Nobuo Serizawa. Only the characters were changed, and the only sci-fi element in the US version is Eagle, the titular Mecarobot. Otherwise, the game remains a generic golf game, and the other three introduced characters are two white women and one white man, replacing the Japanese version's three Asian men.

In an interview with TechRaptor, lead developer Ryan Koons stated that the decision to make HuniePop a gameplay-centric title instead of a story-centric one like other dating sims didn't happen until months into development. The original intention was to make a traditional dating sim, only for Koons – who already had little interest in storytelling in video games – to overhaul the concept due to his growing ennui.

In the same interview, Koons stated that he deliberately sought to avoid many of the cliches associated with dating sims, particularly "the usual innocent waifu style character types." Consequently, the game's cast are based on people from his own life, and the writing is much more irreverent than other dating sims. In particular, Koons described deuteragonist Kyu Sugardust as a raunchy fictionalization of her voice actress, Jaclyn Aimee.

If the player shakes the game camera while over a snow tile, it will cause the snow to swirl around much like when a snow globe is shaken.

Performing El Blaze's item win pose with the maracas will feature Amigo from Samba de Amigo popping out of the maracas.

One of Kage's item win poses features him throwing a pan into the air and it landing on his head. This is a reference to a secret win pose he had in Virtua Fighter 3tb.

In Virtua Fighter 3tb, Jacky and Kage both have a secret win pose when holding Down, Guard, Punch, and Evade. They will perform "V for Victory" poses. If Kage is in his 2P costume and gets an "Excellent" victory on Akira's stage, he will perform a secret win pose where a metal pan will fall on his head.

In 2013, Square Enix published a novella titled "Final Fantasy X-2.5 ~Eien no Daishō~" ("Price of Eternity"), made to commemorate the release of the Final Fantasy X/X-2 HD remasters that year. It was written by both games' scenario writer Kazushige Nojima. The novella never received an official English release, and the only existing fan translation as of 2024 was translated from Japanese to French to English. The book was heavily criticized worldwide upon release for its contents, vague writing style, introducing violent and sexual elements uncommon to the Final Fantasy series at the time, and weakening the impact of both games' endings. For context, X's plot builds up to Spoiler:a negative ending where Tidus dies and Yuna has to accept his death and move on in life, while X-2 renders this moot, turning it back around to Spoiler:a positive ending centering on the possibility that Tidus is still alive and bringing him back to life at the end of the game. What X-2.5 does to weaken this is Spoiler:immediately kill Tidus and immediately resurrect him for the express purpose of setting up future stories, removing the emotional weight and finality of him being truly dead or alive.

X-2.5's plot takes place between the first ending of X-2 and its secret ending. It has two sections written from Tidus and Yuna's own perspectives before shifting to a section with both of their perspectives. After reuniting, Yuna is briefly separated again to address recent developments on Besaid Island. Tidus later goes sailing to look for her, falls asleep, and wakes up finding her in the boat. Spoiler:On their way back to Besaid, they get lost in a storm and are marooned on an island resembling Besaid, having transported 1000 years back in time. While there, Tidus inexplicably gets hit in the head with an object resembling a Blitzball that is actually a bomb. When he goes to pick it up, it suddenly explodes, decapitating Tidus and sending his head flying near Yuna with a surprised expression on his face. Yuna faints and sees a vision of a god-like figure who helps her resurrect a ghost-like version of Tidus through Beckoning, where someone thinks of a person they knew who died, summoning an illusion of them made of Pyreflies from the Farplane, but if that illusion learns they are not actually alive, they will fade away.

The rest of the story involves Yuna Spoiler:going back and forth from the past to present trying to keep Tidus' spirit from vanishing by interacting with several new characters, Briar and Kush, who also turn out to be Beckoned spirits from the past and vanish at the end of the book, and Ifarnal, a summoner who tells Yuna that Tidus must kill Kush if they want to return to the present together and later gets killed by another bomb. Through the subplot with these new characters, the novella establishes that one way to create "cores" used to summon Aeons (of which the Aeon Cores are established to be very similar to Faytes but also have several differences) is implied to be through consensual sex (in a scene where Yuna is transferred the knowledge on how to create them and blushes in embarrassment). At the end of the book, there is a small time-skip that occurs that shows Tidus and Yuna during the secret ending of X-2, showing it in a different context now knowing the events of the book, and ends on the implication of further continuations to the story.

This story would later be continued with Final Fantasy X-2: Last Mission, which came out years before X-2.5 and does not acknowledge the events of it, but the HD remaster does include a continuation to both that is relevant to the events of X-2.5. It is a 30-minute audio drama that was dubbed internationally called "Final Fantasy X -Will-" and was also written by Nojima. The story follows two summoners, Chuami, claiming to be the daughter of Auron, and her assistant Kurgum, who gradually meet the cast of the game as new events occur. Yuna discovers Spoiler:that several souls are being beckoned back from the Farplane, including Sin. In what seems to be an effort to prevent the still-ghostly Tidus from sacrificing himself to kill Sin again, she breaks up with him by lying about being in love with another man, and the summoners go off to fight Sin, appearing to set up the plot for a potential Final Fantasy X-III.

In the "3rd Mix PLUS!" variant of this game, there is unused data for the song "TOTAL RECALL" by ULTIMATE HEIGHTS. This includes unused graphics, step charts and lyrics for the song.

The Art of Fighting ending, which was a continuation from the ending from The King of Fighters XIV, features Khushnood from Garou: Mark of the Wolves. However, his name changed to Marco in this ending, which was his original name in the Japanese version of Garou: Mark of the Wolves. This was likely due to The King of Fighters XIV's director, Yasuyuki Oda, and art director, Nobuyuki Kuroki, asking on a livestream with SNK community manager KrispyKaiser if the fans would like his original name in future games. The chat overwhelmingly preferred the name Marco.

The Ziggy enemies appear to be modeled after Ziggy Stardust, a stage persona created and portrayed by English rock musician David Bowie from 1972 to 1973. In addition to the identical names, the Garden Ziggy variety features brightly colored lightning bolts painted across each eye and a large yellow mohawk, with the results resembling the cover photo for Bowie's 1973 album Aladdin Sane (which depicts Bowie with a red lightning bolt on one eye and a large red mullet).

In PAL releases of the PlayStation 2 version, the player is normally only able to access the tutorial in English, French, Italian, Castilian, and Dutch. Despite this, versions in the other supported languages (German, Swedish, Finnish, Danish, Norwegian, and Portuguese) are present in the game's data and can be accessed either through hacking the game or selecting a supported language and switching to an unsupported one with debug features just before the screen fades to black. It is unknown why these six variants of the tutorial were made inaccessible in the final game, given that they are fully translated.

Temjin, from Art of Fighting 2, and Mars People, from Metal Slug 2, make a cameo appearance in the "Friendly Fight" ending.